This application claims the priority benefit of Taiwan application Ser. No. 87104157, filed Mar. 20, 1998, the full disclosure of which is incorporated herein by reference.
1. Field of the Invention
This invention relates to security monitoring systems, and more particularly, to an addressable security monitoring system.
2. Description of Related Art
Security monitoring systems are customarily installed in places such as banks for the purpose of allowing the security guards to visually observe remote sites for criminal actions. Typically, a security monitoring system includes a number of video cameras that are connected via cables to a monitor installed in the security guard room. By conventional technology, each of the video cameras is connected via a dedicated cable to the security guard room. Therefore, if a great number of video cameras are installed, the total number of cables required to connect these video cameras to the security guard room is correspondingly large. The handling and arrangement of such a great number of cables is undoubtedly a laborious and troublesome task. A conventional security monitoring system is illustratively depicted in the following with reference to FIG. 1.
FIG. 1 is a schematic block diagram showing the configuration of a conventional security monitoring system. As shown, the security monitoring system includes a monitor 13, a switching circuit 11, and a plurality of video cameras connected respectively by a plurality of dedicated cables 15 to the switching circuit 11. In practical use, the switching circuit 11 and the monitor 13 are installed, for example, in a security guard room 14, while the video cameras 12 are installed at those places that are to be under surveillance. Each of the video cameras 12 is installed at a particular place for the purpose of allowing the security guard in the security guard room 14 to visually observe that place for possible criminal or unauthorized actions. The switching circuit 11 operates in a time-sharing multiplex manner that allows the video cameras 12 to be connected alternately to the monitor 13. The captured video images from these video cameras 12 can be either alternately displayed on the monitor 13, or simultaneously displayed together in partitioned blocks on the screen of the monitor 13. One drawback to this security monitoring system, however, is that, each of the video cameras 12 is connected by one dedicated cable to the security guard room 14. Each time one additional video camera is installed, it has to be connected by one additional cable to the security guard room 14. The total number of cables is therefore very large, which makes the handling and arrangement of the security monitoring system a very laborious and troublesome work. Moreover, in the event that the security guard room 14 is to be relocated to another site, the rearrangement of the cables would involve very laborious work.
It is therefore an objective of the present invention to provide a security monitoring system with addressable capability, which allows all of the video cameras in the system to be connected via only one single cable to the security guard room so as to allow a considerable simplification in the cabling of the security monitoring system and thus a considerable reduction in the installation cost.
In accordance with the foregoing and other objectives of the present invention, a security monitoring system with addressable capability is provided. The security monitoring system of the invention comprises the following: a cable having a first end and a second end; a central control unit connected at the first end of the cable, capable of issuing a first signal; at least one addressable video camera connected at the second end of the cable to be connected to the central control unit; and a monitoring device for displaying a second signal. The addressable video camera receives the first signal from the central control unit and compares the first signal with a preset value. If these match, the addressable video camera sends out a second signal via the cable back to the central control unit. The second signal is then displayed by the monitoring device.